Click the blue region and drag the mouse button to move the flashlight.Click the green region and drag the mouse button to change the direction of the flashlight.Some of the light were reflected back to the water,

and some of the light beam change their direction (refracted) into the air.

When the angle is large enough, the refraction beams vanished ( Total internal reflection).Click the blue region twice, and the flashlight will turn into a laser pointer.

You can move or change direction of the the laser point with similar way as metioned above.

In laser pointer mode: click the water/air interface will change the property of the interface. Toggle between flat surface/rough surface.

In rough surface mode: watch the diffuse reflection.

In flat surface mode: a circle will be shown while drag the mouse button.

the length of yellow bar = the length of orange bar => law of reflectionThe length of red bar/the length of yellow bar = constant (index of refraction) => law of refraction (Snell's law).

Click the blue region of laser point to change back to flashlight mode.

Subject: Refraction Applet Date: Thu, 23 Apr 1998 10:14:02 -0400 From: Sandee Coats-Haan <LA_COATSHAA@PO.SWOCA.OHIO.GOV> To: hwang <hwang@phy03.phy.ntnu.edu.tw> Is there any way to change the velocity vector and/or the medium thickness on your refraction applet if you don't have a two button mouse? Sandee (Lakota East High School Physics) P.S. -- you have an incredible site

Subject: (no subject) Date: Wed, 29 Apr 1998 22:13:08 -0500 From: Dion Sanchez <dion@insync.net> To: hwang@phy03.phy.ntnu.edu.tw I want to thank you for this page, it has helped me visualize what a text book could not. I have been looking for something like this for a long time. great stuff thanks. dion

i want to make a wesite of the physics based on x xi xii class label.i have need cd and study material if u have then please try to mail or send me thats i can give in india powerfull. deepak kumar 236,Triveni appt.jhilmil colony new delhi india-1100095 ph.no:-+91-11-22158693,9312271784

I had a problem to run the applet offline. May be the solution I found is useful to some people.

I think I had a compatibility problem with Java from Sun microsistems. I had to manually disable the Sun Java Console in the Internet Explorer. This can be done at Tools->Options-Advanced->Java > (Sun).

I am not familiar to Java. May be some one can shed more light to this type of problems.

I am very interested in your applets, besides i am from Lithuania But i have very big question, i think this applet shows wrong angles, is any chances that you could fix it? I don't think that the angle can be more than 90 degree, and it shows more than 100.

I can add those angles easily. But do you know why I did not do it that way? Because I think what students will get are just two numbers. Is it really better that way?I hope we can discuss: Is it better to show those two angles? Especially, you want it to be shown in degree.

The real physics meaning of refraction law is the ratio of those two distances is a constant. That is why I draw those two lines and show their distance. And I hope students to find out the relations (for reflection and refraction cases). And I think this is more important than just showing two numbers.

It is more difficult for student to find relation between those two numbers , especially if there were shown in degree. Even there were shown in radian, the relation between those two number is n1*sin(c1) =n2*sin(c2).Can student find more physics meaning with those numbers shown in applet?

I think we should keep the current version: The ratio of those two distances (horizontal displacement) is a constant. And this is the physics of the refraction law.

n1*sin(c1) =n2*sin(c2) is a mathematics relation.L1 and L2 are the distances shown in the applet.sin(c1)=L1/R, and sin(c2)=L2/RSo n1*L1=n2*L2 is the result of refraction law.Or L1/L2=n2/n1 which is a constant.

This is the reason why the applet was designed this way, and why I draw a circle to help students to find relation between those two distances when light is refracted (Law of refraction) --- It is also the meaning of sin(c).

Yes for sure i would like to have a discussion. i have understood the meaning of sin (c1)*L1/R and sin(c2)= L2/R. But how can i tell what is R ? i am trying to understand, but i can't find the way? could you tell me?

R is the radius of the circle, and it can be any number which is greater than zero.The ratio of L1/R is the same (mean the same angle).

For example: if you only have index of refraction for both media, and you do not have a calculator to calculate the value of sine function.You can draw a circle with any radius R. With any incident ray, draw the horizontal displacement L1. Then you know how to find the outgoing ray: the one with horizontal displacement L2=n1*L1/n2.

And I believe if you ask students to do this kind of exercise by hand, they will remember the refraction law.

Amazing demo. I find this website is definitely of Ace class. This is just a suggestion of considering negative index in which the students may be interested. It is good to give them some exposure to this topic now, i suppose.CW

Subject: Physics of Light Date: Tue, 5 Jan 1999 21:13:57 -0400 From: "Reg & Lori Coppicus" To: Sir; Enjoyed very much the physics of led light showing internal reflection, and diffusion of the laser. I look forward to examining more related Java applications, but a very good presentation.